Igneous
Pumice
Pumice (Amorphous volcanic glass)
Hardness: 5-6 (scratched by steel); Color: Light gray to white; Luster: Pearly to dull; Texture: Vesicular (full of holes); Density: Typically floats in water.
- Hardness
- 5-6 (scratched by steel)
- Color
- Light gray to white
- Luster
- Pearly to dull
Identified More igneous →
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Physical properties
Hardness: 5-6 (scratched by steel); Color: Light gray to white; Luster: Pearly to dull; Texture: Vesicular (full of holes); Density: Typically floats in water.
Formation & geological history
Formed when highly pressurized, gas-rich magma is violently erupted from a volcano. The rapid cooling and depressurization trap gas bubbles as the lava solidifies into glass.
Uses & applications
Used as an abrasive in polishing, skin exfoliation (pumice stones), lightweight aggregate in cement, and in horticulture to aerate soil.
Geological facts
Pumice is the only rock that floats on water. The location provided (Northern Kentucky) is entirely sedimentary, meaning this volcanic rock was likely transported there by humans for landscaping or driveways rather than occurring naturally.
Field identification & locations
Identify by its light weight (low density), light gray color, and sponge-like texture. Feel for a rough, abrasive surface. Common in volcanic regions but out of place in Kentucky.
